Brake failure warning device with relatively movable detented contact bars actuatable by different pressure sources

ABSTRACT

A dual plunger differential pressure indicating device for use in a ground vehicle having separate hydraulic braking systems for the front and rear brakes thereof which will indicate the occurrence of a malfunction in either one of the hydraulic braking systems. The indicating device includes a detent latching device for maintaining the indicating device in an activated position and mechanism for hydraulically resetting the device after correction of the malfunction.

United States Patent 72] Inventor Howard R. Jilbert Saint Joseph, Mich.[21] Appl. No. 86,689 [22] Filed Nov. 4, 1970 [45] Patented Jan. 11,1972 [73] Assignee The Bendix Corporation [54] BRAKE FAILURE WARNINGDEVICE WITH RELATIVELY MOVABLE DETENTED CONTACT BARS ACTUATABLE BYDIFFERENT PRESSURE SOURCES 12 Claims, 3 Drawing Figs.

52 vs. (:1 200/83 R, 200/82 D, 200/83 A, 200/l66 SD [5i] lnt.Cl .H0lh35/26, HOlh 35/34, HOlh 35/38 [50] Field of Search 200/82 D, 83 R, 83 J,153 LA, 83 E, 83 A, 166 SD, 83 H [56] References Cited UNITED STATESPATENTS 2,435,143 l/1948 Knauth, 200/83 J 2 ,630,499 3/1953 Weld .5.ZOO/166 SD 3,011,595 12/1961 Heiss et a1 ZOO/83 H 3,228,194 1/1966 BlairZOO/82 D UX 3,314,047 4/1967 Zincke et al.. 200/83 R X 3,382,333 5/1968Ihnacik,.1r ZOO/82 D FOREIGN PATENTS 1,120,862 7/1956 France 200/83 HPrimary Examiner- Robert K. Schaefer Assistant Examiner-Robert A.Vanderhye Att0rneysW. N. Antonis and Flame, Hartz, Smith and Thompson 9oT- l l l l 84 68 1 ,ga 72 76 E //4 46 7870 //6 54 50 52 50 I 1 e i y 4230 32 :44 36\ PATENTEn mu 1 I972 SHE! 1' ATTORNEYS PATENIEU JAM 1 am ame -an m 2 T u m M 0 a Q w M ATTORNEYS BRAKE FAILURE WARNING DEVICE WITHRELATIVELY MOVABLE DETENTED CONTACT BARS ACTUATABLE BY DIFFERENTPRESSURE SOURCES BACKGROUND OF THE INVENTION This invention relates towarning devices for indicating loss of pressure in one side of a dualhydraulic vehicular braking system.

In a vehicle having a split system master cylinder, two separate fluidsystems connect the master cylinder to a respective set of front andrear brakes for simultaneously activating the same. If the hydraulicsystem for one set of brakes should fail, the other set of brakes willstill operate. While greater pedal effort is required to stop a vehicleby using only one set of brakes, the operator might not realize that oneof the hydraulic systems is inoperative. It is, therefore, desirable toprovide a warning device in the drivers compartment to indicate afailure in the brake system. However, most existing warning devicesoperate only while the brakes are applied. Even if one of the systemshas failed completely, the vehicle operator is apprised of this factonly during a brake application. Or if the failure indication remainsactivated upon release of the brakes, it also persists even afterpressure to the defective system has been restored until the warningdevice is reset by a mechanic. It is, therefore, desirable to provide awarning device that, once activated by a failure in the hydraulicsystem, continuously warns the driver of the existing failure until thedevice automatically resets when the system is repaired.

SUMMARY OF THE INVENTION It is an object of this invention to provide afailure warning switch for use in a dual hydraulic vehicular brakingsystem which is capable of indicating any predetermined excessivepressure differential between the two hydraulic brake systems resultingfrom fluid loss or pressure loss in one of the systems.

It is an important object of this invention to provide a brake failurewarning switch which will automatically reset to its normal, nonactuatedposition upon restoration of normal brake application fluid pressure inall systems without disassembly of the switch itself or bleeding of thebrake lines.

It is a further object of this invention to provide a brake failurewarning switch which will maintain any failure indication continuouslyuntil normal brake application fluid pres sure is restored to allsystems.

It is a still further object of this invention to provide a brakefailure warning switch which minimizes the possibility of cross leakageof hydraulic fluid from one system to the other and from either systeminto the electrical mechanism.

It is a further object of this invention to provide a relativelyinexpensive detachable component brake failure warning switch of thetype described, which includes a minimum number of parts and is remotelylocated from other associated mechanisms for easy replacement, repair,or maintenance.

It is another object of this invention to provide a brake failurewarning switch for use in a braking system which has a more simplifiedconstruction and a lower actuation displacement loss than previous brakefailure indication systems.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of my brakefailure warning device shown in conjunction with a hydraulic brakingsystem;

FIG. 2 is a perspective view partially in section of another embodimentof my brake failure warning device; and

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, fluidpressure is developed in a master cylinder by operation of a brake pedal12 mounted in the vehicle operators compartment. Master cylinder 10 isof the split system type and therefore develops pressure in each of apair of hydraulic systems 14 and 16 to actuate front and rear brakes 15and 17, respectively.

Each of the hydraulic systems 14 and 16 are connected to separatesensing systems of a differential pressure warning switch 18 which ismounted at any convenient location on the vehicle such as the firewall,where the switch 18, may be grounded.

Switch 18 includes a housing 20 defining passages 22 and 24 therewithincommunicating with inlet ports 26 and 28 which are connected to thecorresponding hydraulic systems 14 and 16, respectively. Passages 22 and24 communicate with cavities 30 and 32 which contain diaphragms 34 and36. Diaphragm cavities 30 and 32 communicate with bores 38 and 40 withinwhich cylindrical plungers 42 and 44 reciprocate in abutting contactwith diaphragms 34 and 36. Bores 38 and 40 include at their upper ends,as illustrated by FIG. 1, bore portions 46 and 48 which operativelyretain return springs 50 and 52. Located intermediate the bore portions38 and 46, and 40 and 48, respectively, are angular cavities 54 and 56which contain actuating levers 58 and 60 pivotally mounted therein atpoints 59 and 61, respectively. The levers 58 and 60 are urged againstshoulders 62 and 64 of the cavities by springs 50 and 52 when there isno pressure in either hydraulic system. Intermediate the bores 46 and 48is an elongated cavity 66 within which contact bars 68 and 70 areslidably mounted. Contact bars 68 and 70 are interconnected at theirlower extremities, as viewed in FIG. 1, with the actuating levers 58 and60 respectively, and have contact springs 72 and 74, respectively,conductively afiixed thereto. Contact bar 70 has a detent 78 thereon.Contact bar 68 includes an insulator 76 and two notches 80 and 82 on theface thereof which mechanically retain detent 78 upon a predeterminedamount of relative movement between the bars.

At the top end of the housing 20, as viewed in FIG. 1, are twoelectrical terminals 84 which are affixed in such a way as to beinsulated from each other and have contact strips 86 conductivelyfastened to the ends of the terminals 84 which are connected in serieswith the contact springs 72 and 74; with the contact bars 68 and 70;with a failure indicator 88; with the vehicles battery 90; and with anelectrical ground 92.

DESCRIPTION OF THE ALTERNATE EMBODIMENT Referring to FIGS. 2 and 3, itwill be noted that like parts are designated by like numerals plus 100.

Switch 118 includes a housing 120 defining passages 122 and 124 (onlyone of which illustrated) therewithin communicating with inlet portports 126 and 128 which are connected to the corresponding hydraulicsystems 114 and 116, respectively. Passages 122 and 124 communicate withcavities 130 and 132 (only one of which is shown) respectively, withinwhich diaphragms 134 and 136 (only one of which is shown) areoperatively carried. Diaphragm cavities 130 and 132 communicate withbores 138 and 140 (only one of which is shown) within which cylindricalplungers 142 and 144 reciprocate in abutting contact with diaphragms 134and 136, respectively. The other ends of the plungers 142 and 144 (onlyone of which is shown) are pressed against actuating levers 158 andwhich are pivotally connected to the housing 120 by insulated pivot pin159 and spacer 194 which maintain electrical isolation between the twoactuating levers 158 and 160. At the distal portions of actuating levers158 and 160 opposite the ends against which the plungers I42 and 144press, contact bars 168 and 170 are affixed. Contact bar 170 has adetent 178 located thereon. Contact bar 168 includes an insulator 176and two notches 180 and 182 serving to mechanically retain detent 178upon a predetermined amount of relative movement between the bars 168and 170.

Permanently mounted in the housing 120, are electrical terminals 184which are electrically insulated from each other and have a recessedannular channel 196 and a center pilot post 198 included on theirinterior portion, as viewed in FIG. 2, for the purpose of retainingelectrically conductive return springs 150 which are connected in serieswith the terminals 184, with the actuating levers 158 and 160, with thecontact bars 168 and 170, with a failure indicator 188, with thevehicles battery 190, and with a suitable electrical ground 192.

MODE OF OPERATION Assuming no malfunction in the brake hydraulic systemthe contact bars 68 and 70 are juxtaposed in such a way that detent 78presses against insulator 76 and insulates the switch 18, from theground 92 thus causing the electrical circuit through contact spring 72,contact bar 68, contact bar 70, contact spring 74, contact strip 88, oneof the terminals 84, the indicator 88, and the vehicle's battery 90, toremain open. In this nonactuated operational mode, the indicator 88 willnot function. However, if a malfunction in either of the hydraulicsystems 14 and 16 occurs, causing a loss of pressure at one of the inletports 26 or 28, pressure in the other port causes the associateddiaphragm 34 and 36 to move upward against the plunger 42 or 44. This inturn forces the actuating lever 58 or 60 to swing about pivot point 59or 61, thus shifting either contact bar 68 or 70 with respect to theother. Such relative movement causes detent 78 to be lodged in notch 80or 82 and the switch 18 is in an actuated operational mode position. Anelectrical circuit is completed through the contact bars 68 and 70,contact springs 72 and 74 contact strips 86, and terminals 84 to theground 92 from the batter 90, thus causing indicator 88 to function.

Upon release of the brakes, stored energy of the return spring 50 and 52acts to return the contact bars 68 and 70 and associated linkage, i.e.,actuating levers 58 and 60, plungers 42 and 44 and diaphragms 34 and 36,to their base positions. The force of this thrust is not great enough,however, to cause the detent 78 to be dislodged from notch 80 or 82 sothat the switch is mechanically latched in the closed position by theforce of contact springs 72 and 74 and the failure indicator 88 remainsenergized.

When fluid pressure is restored in the malfunctioning system, bothdiaphragms 34 and 36, plungers 42 and 44, and actuating levers 58 and60, move upwardly in unison until the uppermost contact bar 68 and 70reaches the limit of its travel. Either contact bar 68 or 70 reaches thelimit of its travel. Either contact bar 68 or 70 could be uppermostdepending upon which hydraulic system pressure failure caused thefailure mode positioning of the switch, i.e., whether detent 78 islodged in notch 80 or 82. As hydraulic pressure continues to rise theother contact bar 68 or 70 is pushed upward in cavity 66, as viewed inFIG. 1, and detent 78 is disengaged from notch 80 or 82 and urged ontoinsulator 76, thus breaking the electrical circuit and deactivating theindicator 88 while automatically resetting the warning switch 18.

In the embodiment of FIGS. 2 and 3, movement of diaphragm 134 or 136with respect to the other causes the associated plunger 142 or 144 andactuating lever 158 or 168 to move causing detent 178 to move frominsulator 176 into notch 180 or 182, depending upon which hydraulicsystem pressure has failed to complete an electrical circuit from theelectrical ground 192 through the terminals 184, the return springs 150,actuating levers 158 and 160, and contact bars 168 and 170 to thevehicle battery 190 and thereby actuate indicator 188. The spring actionof actuating levers 158 and 160 maintain engagement of the detent 178 inthe notch 180 or 182 until normal system fluid pressure is restored,thus mechanically latching the switch in the actuated or failureoperational mode position. Restoration of fluid pressure to both inletports acts to disengage detent 178 from notch 180 or 182 to repositionthe detent 178 or insulator 176 by moving the diaphragm 132 or 134,depending upon which hydraulic system failure caused the failure modepositioning of the switch. At the same time one of the plungers 142 or144 will move upward, as viewed in FIG. 2, with respect to the otherplunger 142 or 144, thus causing contact bar 168 or 170 to movedownward, as viewed in FIG. 2, with respect to the other contact bar 168or 170 through the motion of actuating lever 158 or 160 about pivot pin159. This occurs as the result of urging by the plunger 142 or 144against the actuating lever 158 or 160, thus automatically breaking theelectrical circuit and deactivating the indicator 188 while resettingthe warning switch 118 in its base position.

lclaim:

1. In a fluid system having first and second sources of fluid pressure,a differential pressure indicating device comprising:

a housing having first and second pressure-responsive means locatedtherein, one of which is operatively connected to and moveablyresponsive to said first source of fluid pressure and the other of whichis operatively connected to and movably responsive to said second sourceof fluid pressure;

electrical switch means located in said housing and having a pair ofcontact bars, one of which is operatively connected to and movable withone of said pressure-responsive means and the other of which isoperatively connected to and movable with the other of saidpressureresponsive means; and

detent means formed on said contact bars for activating a warning signalupon relative movement between said bars;

said detent means moving from a nonlatching to a latching position uponrelative movement of said bars to provide a continuous warning signaluntil predetermined pressures are subsequently applied to said first andsecond pressure-responsive means.

2. A differential pressure indicating device, as defined in claim 1,wherein said housing includes first and second ports communicatingrespectively with said first and second sources of fluid pressure, firstand second bores connected respectively to said first and second ports,and a cavity located intermediate said bores;

said first and second pressure-responsive means includes first andsecond plungers respectively slidable in said first and second bores,one of said plungers being operatively connected to one of said contactbars to cause movement thereof and the other of said plungers beingoperatively connected to the other of said contact bars to causemovement thereof; and

said contact bars are located in said cavity.

3. A differential pressure indicating device, as defined in claim 2,which includes lever means located between said plungers and saidcontact bars for transmitting motion from said plungers to said contactbars.

4. A differential pressure indicating device, as defined in claim 3,which includes first resilient means for opposing movement of saidplungers.

5. A differential pressure indicating device, as defined in claim 4,wherein said first resilient means are located in said bores.

6. A differential pressure indicating device, as defined in claim 4,which includes electrical circuit means for activating said warningsignal, wherein said first resilient means is located in said housingand is a component part of said electrical circuit means.

7. A differential pressure indicating device, as defined in claim 4,which includes second resilient means located in said cavity for urgingsaid contact bars toward each other.

8. A differential pressure indicating device, as defined in claim 7,which includes electrical circuit means for activating said warningsignal wherein said second resilient means is a component part of saidelectrical circuit.

9. A differential pressure indicating device, as defined in claim 8,which includes diaphragm means in contact with the ends of said firstand second plungers and located between said first and second ports andsaid first and second plungers, respectively, to isolate said first andsecond sources of fluid pressure from said electrical switch means andprevent cross leakage between said pressure sources.

10. A differential pressure indicating device, as defined in claim 9,wherein said lever means includes a first lever located between saidfirst plunger and one of said contact bars and a other of said contactbars, said first and second levers each having one end thereofoperatively connected to its associated plunger, the other end thereofoperatively connected to its associated contact bar, and an intermediateportion thereof pivotally connected to said housing.

12. A differential pressure warning switch, as defined in claim 11,wherein said lever means is a component part of said electrical circuitmeans.

@35 UNITED STATES PATENT OFFIQE QERHNCATE 0F fiQRREC'NON Patent No. 3,63,639 Dated January i I 1372 Inventofls) Howard R. Ji lbert It iscertified :that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

E.- Co! umn 3, Lines 38 and 39: delete "Either contact bar 68 or .1 Y 70reaches the I imit of its travel Signed and sealed this 19th day ofDecember 1972.

( A Attest 2 EDWARD M.FLETCHER, JR. ROBERT GOITSCHALK Attesting OfficerCommissionerof Patents mg UNMED STATES PATENT @FFIQE @ERTENQATE 0FQQRREMWN Patent No. 3,63 ,639 Dated January i I I972 Inventor(s) HcwardJ5 lbert It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Coi umn 3, Lines 38 and 39: delete "Either contact bar 68 or W 70reaches the limit of 'its travel."

Signed and sealed this 19th day of December 1972.

(SEAL) At test EDWARD M.FLETCHER, JR. v v ROBERT GOTTSCHALK AttestingOfficer Commissioner of Patents

1. In a fluid system having first and second sources of fluid pressure,a differential pressure indicating device comprising: a housing havingfirst and second pressure-responsive means located therein, one of whichis operatively connected to and moveably responsive to said first sourceof fluid pressure and the other of which is operatively connected to andmovably responsive to said second source of fluid pressure; electricalswitch means located in said housing and having a pair of contact bars,one of which is operatively connected to and movable with one of saidpressure-responsive means and the other of which is operativelyconnected to and movable with the other of said pressure-responsivemeans; and detent means formed on said contact bars for activating awarning signal upon relative movement between said bars; said detentmeans moving from a nonlatching to a latching position upon relativemovement of said bars to provide a continuous warning signal untilpredetermined pressures are subsequently applied to said first andsecond pressureresponsive means.
 2. A differential pressure indicatingdevice, as defined in claim 1, wherein said housing includes first andsecond ports communicating respectively with said first and secondsources of fluid pressure, first and second bores connected respectivelyto said first and second ports, and a cavity located intermediate saidbores; said first and second pressure-responsive means includes firstand second plungers respectively slidable in said first and secondbores, one of said plungers being operatively connected to one of saidcontact bars to cause movement thereof and the other of said plungersbeing operatively connected to the other of said contact bars to causemovement thereof; and said contact bars are located in said cavity.
 3. Adifferential pressure indicating device, as defined in claim 2, whichincludes lever means located between said plungers and said contact barsfor transmitting motion from said plungers to said contact bars.
 4. Adifferential pressure indicating device, as defined in claim 3, whichincludes first resilient means for opposing movement of said plungers.5. A differential pressure indicating device, as defined in claim 4,wherein said first resilient means are located in said bores.
 6. Adifferential pressure indicating deVice, as defined in claim 4, whichincludes electrical circuit means for activating said warning signal,wherein said first resilient means is located in said housing and is acomponent part of said electrical circuit means.
 7. A differentialpressure indicating device, as defined in claim 4, which includes secondresilient means located in said cavity for urging said contact barstoward each other.
 8. A differential pressure indicating device, asdefined in claim 7, which includes electrical circuit means foractivating said warning signal wherein said second resilient means is acomponent part of said electrical circuit.
 9. A differential pressureindicating device, as defined in claim 8, which includes diaphragm meansin contact with the ends of said first and second plungers and locatedbetween said first and second ports and said first and second plungers,respectively, to isolate said first and second sources of fluid pressurefrom said electrical switch means and prevent cross leakage between saidpressure sources.
 10. A differential pressure indicating device, asdefined in claim 9, wherein said lever means includes a first leverlocated between said first plunger and one of said contact bars and asecond lever located between said second plunger and the other of saidcontact bars, said first and second levers each having one end thereofpivotally connected to said housing, the other end thereof operativelyconnected to its associated contact bar, and an intermediate portionthereof operatively connected to its associated plunger.
 11. Adifferential pressure indicating device, as defined in claim 9, whereinsaid lever means include a first lever located between said firstplunger and one of said contact bars and a second lever located betweensaid second plunger and the other of said contact bars, said first andsecond levers each having one end thereof operatively connected to itsassociated plunger, the other end thereof operatively connected to itsassociated contact bar, and an intermediate portion thereof pivotallyconnected to said housing.
 12. A differential pressure warning switch,as defined in claim 11, wherein said lever means is a component part ofsaid electrical circuit means.